Quantum dots are nanometer-scale particles (e.g., typically 1–10 nanometers in diameter) of metal, dielectric or semiconductor material. Quantum dots are commonly made of compound semiconductors such as CdSe, ZnSe, or PbS and may be manufactured in solid hosts, films, suspensions or other material formats.
Quantum dots are well known for providing useful optical properties when incorporated into polymeric and glass materials. Specifically, quantum dots can provide optical amplification, saturable absorption, or nonlinear effects for example. As understood in the art, the term quantum dot may apply to particles in the form of spheres, rods, wires, etc. The term ‘quantum dot’ herein refers to any such forms as are known in the art.
U.S. Pat. No. 5,881,200 to Burt, for example teaches an optical fiber with a hollow core filled with a quantum dot colloid. The quantum dots provide an optical gain medium that can be used as a laser amplifier. Similarly, U.S. Pat. No. 5,260,957 to Hakimi et al. teaches a polymeric optical waveguide containing quantum dots that provide lasing capability. U.S. Pat. No. 6,710,366 also teaches matrix composite materials with quantum dots having nonlinear optical properties.
Incorporating quantum dots into optical fibers and waveguides can be problematic because of the sensitive nature of quantum dots. For example, many quantum dots are not able to withstand high temperatures (e.g., above 1000 C) required for melting glass or silica. Specifically, quantum dots from compound semiconductors can dissociate or diffuse into glass at high temperatures. Quantum dots typically cannot be directly incorporated into a silica optical fiber because they will be destroyed during the high heat (e.g. 1500 C) drawing process. Also, quantum dots can be damaged by oxidation.
Many quantum dots provide superior electronic and optical properties when they are coated with a core shell material such as TOPO. Such core shells can prevent oxidation and enhance electron confinement, and may even be essential in some applications. However, core shell materials are often polymeric and are often destroyed by high temperatures.
However, there are many potential applications for optical fibers (particularly glass fibers) having quantum dots. It would be an advance in the art to provide glass optical fibers having quantum dots that retain desirable electronic and optical properties unaltered by high heat. Additionally, it would be an advance in the art to provide new optical fiber structures and materials that are compatible with quantum dots and with conventional optical fibers.